Controlling system for sound recording devices



June 11, 1935.-' F. HAhL I 2,004,893

' C ONTROLLING' SYSTEM FOR SOUND RECORDING DEVICES Filed July 20, 1955 J RECORDER IMIMI- Patented June 11, 1935 UNITED STATES CONTROLLING SYSTEM FOR SOUND RECORDING DEVICES Ferguson Hall, Shenandoah, Iowa Application July 20, 1933, Serial No. 681,388

14 Claims.

This invention is directed to a controlling system for sound recording devices, wherein the sound Waves to be recorded are the controlling factor in the starting and stopping of the sound recording device.

The primary object of the invention is the provision of a system, in the use of which any sound recording machine is automatically set in operation by the origin of the sound waves to be recorded on that machine, with the system also providing for the automatic stopping of the recording machine at the cessation of the sound waves. Thus, for example, in the use of a dictaphone for the recording of the human voice, the initial tones will automatically start the machine for recording purposes and the cessation of such tones will automatically stop the machine.

The system, generally speaking, includes a sound recording mechanism, together with a source of electrical pulsations of the same form as those of the recorded sound, with means responsive to said pulsations for maintaining the latter at a constant amplitude, together with means operated by said pulsations for controlling the operation of the recording mechanism. Therefore, the act of recording and the control of the recording mechanism per se is concurrent with the pulsations.

The invention, therefore, is directed to an automatic volume control, which in turn governs a voice controlled relay or other equivalent mechanically or electrically controlling means for the manual operation of the recorder. The volume control maintains the constant level of the audible frequency waves and the operation of the recorder governing relay is dependent upon this fact.

The invention is illustrated in the accompanying drawing, in which:

Figure 1 is a diagrammatic view of the system in at least a preferred form of the arrangement.

Figure 2 is a diagrammatic view of the tube and circuits through which the relay is controlled, as indicated in Figure 1, this figure showing additionally electrical means for retarding the breaking of the relay or plate circuit in order to prevent the de-energization of the recorder operating mechanism control in the intervals inwhich pulsations are absent from the volume control circuit. 5 l ""l In the system illustrated, I indicates a microphone and 2 a conventional audio-amplifier, connected with the microphone. The audio-transformers 3 and 4 have their primary windings 5 in to be utilized in any conventional or desired man current from the amplifier is impressed on the primary Win-dings. The transformer 3 is designed to multiply the voltage applied to its primary windings and to separate thecurrent of the output of the amplifier from the input circuit of 6" the amplifier tube, indicated at 6. This tube will be hereinafter referred to as the controlled tube. 1 The secondary winding 1 of the transformer 3 is connected to the input or grid filament circuit 8 of the controlled tube 6. In series with this .10 circuit 8 is a battery 9 and a resistor H1. The plate current from the controlled tube 6 .is led through a choke coil ll, preferably wound upon an iron core and of very high impedance. The,

choke coil by reason of current change produces a voltage across the terminals of the coil which is directed through a condenser l2, a battery l3 or,

other source of direct current of sufiicient voltage being utilized for plate power.

The secondary of transformer 4- is connected 20 to the grid filament circuit of what may be termed a controlling rectifier tube I4, having included in the circuit a biasing battery I5. The plate circuit from the tube l4 includes a choke coil IS, the" plate power being provided by a source of direct 25 denser I2. The circuit 2| includes a .bias b tt r 25. The plate current from tube 20 including a supply battery 26 flows through the windings of a relay 21. This relay serves to close a, circuit ,28, having a source of energy 29 and operatingto energize an electro-magnet 3.0 for operating a clutch 3 iintroduced into a mechanical system for actuating a recorder 32, the recording features of which are in circuit with the system beyond the condenser E 2, as shown. Obviously, of course, the

circuit 28 may be utilized to directly actuate 22.

prime mover by which the recorder is directly operated as distinguished from theclutch control= illustrated. The invention is 'to be consideredup to and including the circuit 28 and this circuit is ner and with any necessary mechanical or electrical means for operating the actuating mechanism; of the recorder or other instrument on. whichthe record is to be made.

With particular regardto' the operation, 1 will be apparent that the pulsations from the microphone are amplified and impressed in the primary windings of the transformers 3 and 4. The transformer 3 multiplies the voltage for the grid fila- 5 ment circuit of the controlled tube 6. As understood, complete current is governed and controlled in a large measure by the voltage between the grid and filament. Small variations in grid voltage will cause comparatively large variations in the plategcurrent; Themore negativethe grid :is

with respect-to: the filament, the more the platecurrent is decreased. The bias battery 9 determines a certain definite amount of said current which normally flows when thereis no excitation from the transformer 3.

exciting voltage, the value of the plate current varies. are exact replicas of the pulsationaproduced. by the microphone and such pass'through the choke coil II. The voltage change in current.th-rough the. coil is directed through the condenser I2 and operates the recording mechanism in the recorder 32? The controlling: rectifier tube. M is served from the audio-amplifier. Thebiasing battery, 15,.pro-

videsamegative bias on the grid Iandisofsuch value yas'to just barely shutofi all the current .in theplateicircuit in theabsence of'exciting voltage from the transformer 4; Thus in the absence 30. ,ofiexciting voltage from. the transformer, there is practically no plate current. As the alternating voltage from the transformer 4is applied to the grid, the grid'voltage'alternately becomes .more negative than the cut+oif voltage and alternately less negative thanthecut-ofi voltage. In the 'periods;..where the grid is less negative than the cut-ofi'voltage, the;current will'flow in theyplate circuit. During the period'when the grid ismore negative than the cut-ofi voltage, no plate current 40., .will flow. It follows that the greater the excitation voltage,- the. greater. the amount of. current thatiwill now in the plate. circuit. If there is no plate current flowing, there is novoltage drop acrossresistor 10." Therefore, thisresistor hasno.

45,, eflecton the'controlledtube 6; When plate current is'fiowing, however, and voltage drop occurs irr'resistorrlfl; this voltage; isadded to the bias produced by battery 91in the grid filament circuit of the controlled tube. Obviously, the greater 50. .theinput voltageto transformers 3. and; 4, the greater-the action ofjresistor lfliandthe greater the decrease imampliflcation in'the. controlled tube; ,B'y selection of appropriate values for the I different; components of the circuits, the ampli 55.. .tfl'cation' could be made -.-to.decrease linearly'with respectjto-"the increase in inputvoltage, whereby the :le'velof volume would be practically constant.

The choke coil l6"; and condensers l8 and I 9" iron out the individual pulsations -in* the plate 60, current ofcontrolling tube M: This prevents ch'ahges'in' the plate current-faster than the natural period of "this system. This natural period can be controlled by suitably choosing values,xfor

, example'bymaking .the inductance of. the coil 65., and-thy capacity." of the condensers suitably.

large.

In, connectionwith the tube 20 which controls the relay, or other mechanical power. generation.

for" the recorder, it. will be apparent that the 70. ,transformer 23 'will serve to excite ,the gridcircuit' 2l,ofthe tube 20immediately following the originof soundin the microphone I, Thebias battery" 25 is here, adjusted to. approximately cut ofithe plate current'in the absence of excitation. 311119.. amount. of, plate current: flowing. will of Under application .of;

These slight pulsations inwplate. currentf course, depend upon the amplitude of the exciting voltage from the transformer 23. The plate current will flow through the windings of relay 21 and so control the auxiliary circuit 28 for directly governing the mechanical opera- 5 tion of the recorder.

Provision must be made, of course, for maintaining the voice controlled relay circuit in the absence of pulsations in the volume control circuit.as,for example, betweenwordsrand incident 10 to short pauses in 'the sound delivered to the microphone. This may be accomplished in several: ways, but in accordance with the provision herein it is preferred that such should be accomplished electrically, and for this purpose and 15 referring more particularly to Figure 2, it is to be noted that there is arranged in the grid circuit 2| of the tube 20 van auxiliary circuit including a rectifier 33, a condenser 34, and a resistance 35. The rectifier is so arranged that its directional 20 effectpermits the flowing of positive electricity to thegrid side of thecondenser 34. The exciting voltage from the transformer 23,;will"th'cn. charge the condenser 34.jwith a positive voltage onQthe grid side; This charge cannot leak .ofi. o.wing.. to.. the directional. effect of. the rectifier.3,3...

Thus, during the period of excitation, the .00 denser 34"remains charged positively. on .the grid side and will not interfere. with the, .flow. of plate current. When the excitation stops, ho we.v.er, as.. in the pausesreferred to, the. accumulated charge... on the condenser. 34 is utilized 7 to .maintaincthe. grid positive through thetime lagincident, to, the character of the resistor 35. There is thus. direct provision. for maintaining the. specific. re-.. 35 corder control circuit closed tomaintainthe. re -I- corder in-operation during the relatively, short. intervals. necessitated by pauses in the delivery of the sound waves to the-microphone. Of,course, the character of ;the resistor and :the, relation .of..

, the parts may. bereadily selected to determine.

this, time lag to take careof all ,usual pauses ,I'B: ferred'to; I

1 In a soundrecordingv system, means for" utilizing the sound waves of the sound tobe .re-. corded for producing electrical pulsations,.m eans, for amplifying said electrical pulsations, 5 controlledby the soundwave'afor maintaining the volume level ofthe amplifiedpulsations sub: stantially constant, a recorder fonIreceiving and recording the amplified constant volume electrical, pulsations, means for operating the recordenand. means responsive to the. amplified .constantvok m t ic l ulsat o s. for ao minasaidi n-h t n mean 2; A sound recording system including means. for transposing sound wavesinto electrical pulsations, means for amplifying said. pulsations, means controlled by the sound waves for, maintaining the volume... level substantially constant, arecorder for. receiving and recording the electrical pulsations under amplified constant-vole ume level output, vmechanism for. operating the recorder, means responsive to. theelectrical pul sations .beingrecordedto control the. operating.

'means for, the recorder, andmeansfon utilizing.

I waves.

' 3. In asound recording, system, means. for, utilizing the sound waves-of. the sound-to,.be.. re+ corded. for. producing electrical pulsations, means .for amplifying. said. electrical pulsations,

controlled by the sound waves for maintaining the volume level of the amplified pulsations substantially constant, a recorder for receiving and recording the amplified constant volume electrical pulsations, means for operating the recorder, and a vacuum tube controlled relay for governing said operating means.

4. A sound recording system including means for transposing sound waves into electrical pulsations, means for amplifying said pulsations, means controlled by the sound waves for main taining the volume level substantially constant, a recorder for receiving and recording the electrical pulsations under amplified constant volume level output, mechanism for operating the recorder, a vacuum tube controlled relay to control the operating means for the recorder, and means for utilizing the electrical pulsations being recorded to maintain operative influence on the operating means of the recorder during limited cessation of sound waves.

5. In a sound recording system, a sound recording mechanism, a source of electrical pulsations of the same form as those of the recorded sound, means for amplifying said electrical pulsations, means for controlling the amplification to maintain the same substantially constant for recording purposes on said sound recording mechanism, and means responsive to said constant volume pulsations for directly governing the actuation of the recording mechanism.

6. A system as described in claim 5, wherein said means is in the form of a vacuum tube controlled relay.

7. A system as described in claim 5, wherein said means is in the form of a vacuum tube controlled relay and including means for accumulating a charge during excitation of said vacuum tube controlled relay and releasing this charge for service in maintaining operation of said relay during limited absence of such excitation.

8. In a sound recording system, a recording mechanism, means for utilizing the waves of the sound to be recorded for producing electrical pulsations of identical form, means for amplifying said electrical pulsations, means controlled by the sound waves for maintaining the volume level of the amplified pulsations substantially constant, means for operating the recorder, and means responsive to the amplified constant volume electrical pulsations for governing said operating means.

9. A sound recording system including means for transposing sound waves into electrical pulsations, means for amplifying said pulsations, means controlled by the sound waves for maintaining the volume level substantially constant, a recorder for receiving and recording the electrical pulsations under the amplified constant volume level output, mechanism for operating the recorder, means electrically responsive to the amplified constant volume level electrical pulsations to control the operating mechanism, and additional means responsive to said electrical impulses for maintaining operative influence on the operating means of the recorder during limited cessation of the sound waves, said additional means utilizing said electrical pulsations for creating a charge of electricity and the utilization of said charge to maintain the operative influence on said operating means during cessation of said electrical impulses. r

10. A construction as defined in claim 9, wherein said additional means includes a rectifier for the electrical pulsations, a condenser for accumulating direct currents from the rectifier, and a resister to dissipate the charge over a predetermined period of time.

11. In a sound recording system, means for utilizing the sound waves of the sound to be recorded for producing electrical pulsations, a recorder for receiving and recording said pulsations, an electrical control network including an amplifier tube, an amplification control tube, means for controlling the amplification of said amplifier tube with rectified pulsations from said control tube, a rectifier tube, said rectifier tube being excited and controlled by said pulsations and acting to rectify said amplified pulsations, and means responsive to said rectified pulsations for controlling the motive portions of said recording mechanism.

12. In a sound recording system, means for utilizing the sound waves of the sound to be recorded for producing electrical pulsations, a recorder for receiving and recording said pulsations, an electrical control network including an amplifier tube, an amplification control tube,

means for controlling the amplification of said amplifier tube with rectified pulsations from said control tube, a rectifier tube, said rectifier tube being excited and controlled by said pulsations and acting to rectify said amplified pulsations, an associated circuit including resistance and capacity for creating an electrical charge for governing the grid bias voltage of said rectifier tube. and means responsive to said rectified pulsations for controlling the motive portions of said record ing mechanism.

13. In a sound recording system, a sound recording mechanism, a source of electrical pulsations of the same form as those of the recorded sound, means for amplifying said electrical pulsations, means for controlling the amplification to maintain the same substantially constant, and a vacuum tube controlled relay including means for accumulating a charge during excitation of said vacuum tube controlled relay and releasing this charge for service in maintaining operation of said relay during limited absence of such excitation.

14. In a sound recording system, the combination of a sound recording mechanism, means for utilizing the waves of the sound to be recorded for producing electrical pulsations of identical form, means for amplifying said electrical pulsations, means controlled by the sound waves for maintaining the volume level of the amplified pulsations substantially constant, means for operating the recorder, and means responsive to the amplified constant volume electrical pulsations for governing said operating means.

FERGUSON HALL. [L. 8.] 

